maggots in wine cap mushrooms?

Hi there,

Looking for guidance on maggots in wine cap mushrooms growing in inoculated wood chips. Based on my reading, this sounds fairly (?) normal, but I have some specific questions.

1. Is this entirely common and inevitable i.e. in *every* mushroom, or only some?

2. If this is normal, are we talking about a couple in each mushroom cap or tons? I noticed just one today and threw it outside. I used the mushroom and put the stem in my kitchen compost tin - within a couple hours, the entire compost was SWARMING. And I tried boiling some other stems to try to make mushroom broth and there were like 20 little maggots boiled up in there. Is that level of infestation normal?

Here's a picture with a few of these little white maggots on the mushroom cap (pic #1).

3. Are there ways to detect visually which mushrooms are better/worse? At first I thought maybe the ones with more mottled caps maybe had more maggots? But then I saw them on the nicer-looking caps too. When the flesh is pocked internally (pic #2) is that a sign of maggots? (And is there a way to know without opening up the mushroom?) I had a couple where the stems were hollow (pic #3) - is that a sign of decay or maggots?

For our own use, maybe a couple are OK, but we can't keep up with these mushrooms and have been giving to friends and family. But now that I know, it doesn't feel right to be giving maggoty mushrooms to others!

4. Anything we can do to minimize these maggots, realistically, without major interventions? Does it make a difference how we store the mushrooms after picking them? These were in the evening after picking them this morning - same day.

Just a sense of scale on what's normal and whether there's a realistic way to give friends mushrooms from our garden that aren't crawling with maggots.

Hi Boris! I haven't experienced this in the couple years I've grown wine caps. How soon after the mushrooms emerge are you picking them?
I always had the best luck with ones that were still in the button stage with more of the wine color. Usually had to be the same day they emerged or not long after. Ones that got away from me and had time for the tops to flatten out or turn up at the edges tended to be a little too funky. I stuffed those back under the wood chips to keep the mushrooms spreading. I would suspect maggots might be more likely in ones that were older and starting to decay.

Hey Boris - I feel your pain. Our wine caps (and oysters, and pretty much any soft-fleshed fungal bodies) get pretty infested with maggots. It seems to be worse in warm weather, and I have noticed that the initial flush in a given spot is more likely to be free of them than subsequent ones. The adult flies may not be very strong fliers.

My main strategy is to do daily checks of the places where I think they're going to pop up and try to pick them on the early side, before they get riddled. I wonder if it's worth trying to put a fine mesh over them when they first emerge to give them an extra day to grow before picking...this will be the next experiment. I don't know what preys on, traps, or discourages the adults from coming and laying their eggs, but if there are biological controls that would be nice.

I've found them in very young mushrooms.  Do the maggots come up from below or down from the cap?

Mike, I think these eggs get laid on the cap. At least that's the case if they're the eggs of flies or flying beetles, which are the most common ones I see referred to as pests of edible fungi. There is also the Sciarid genus of flies, commonly called fungus gnats, who lay eggs on the ground and their larvae burrow in search of mycelium.

Hi Boris,

Yep, maggots sure like Wine Caps.  My personal experience is that the maggots are the worst when I get a huge flush of mushrooms.  And Wine Caps are notorious because they grow so very fast that it is hard to pick them young enough to eat.  And when I get a bed that produces for something like a month, the actual mushrooms grow far faster than I can pick them and the flies are just waiting.

So my suggestion is to pick the Wine Caps when they are the size of a ping-pong ball.  They taste best then anyways.  This gives you better mushrooms and denies them to those pesky flies and their maggots and then the flies don’t get all obsessive about your mushroom patch.

I hope this helps and please keep us updated!

Eric

Aside from all of the good advice on harvesting in the button stage, the storage issue should solve the other 50% of the problem.

Before placing your pick into a basket with clean mushrooms, first shave the bulbous base with a sharp knife or simply cut above the dirt line. Then brush off your mushroom with a clean paint brush to remove any remaining dirt or other matter that can't be seen with the naked eye. ( i.e. fly larva )

Immediately slice your mushrooms into 1/2" thick strips and place into food dehydrator or oven rack on low heat as a last resort. The quick dehydration will arrest the development of any fly larva. Now let cool and place in airtight container for storage in pantry.

Since mushrooms are 90% water, they will really shrink and concentrate the flavor. A little bit goes a long way into soups and other dishes. The dehydrated mushrooms will utilize much less storage space and have a long shelf life as compared to their fresh counterparts.

For best results, washing is not recommended. Remember that you will be cooking the mushrooms later, which kills harmful bacteria and makes mushrooms more digestible. Rehydration and cooking techniques is yet another topic...

When you have sliced your mushroom strips, you can also set aside some to sauté fresh after visually inspecting them.

By the way, flies and gnats are not the only insects feeding on mushroom mycelium, which is also the preferred food for yes bees! Bees move aside the wood chips and consume the little water droplets forming on the mycelium. The polysaccharides in this extract protect the beehive from disease. So by propagating the mushrooms in your garden or food forest, you are inadvertently saving the bees from extinction...

Thank you everyone for your replies. I'm glad to hear that I'm not alone with these maggots. We had stored them in a plastic bag in the fridge, so now I know to stick with paper bags. Also pick early, not when they're the size of a child's face This morning I went out and picked a bunch, much smaller, and put them in a paper bag.

William - I'm looking forward to watching the Paul Stamets video, and very cool about the bees eating the water on the mycelium!

I just bought some wine cap spawn at a farmers' market yesterday, so this is all really good to keep in mind! Thanks!

Harvesting my first Winecaps. Some had a few worm holes, but happily these huge ones were worm free. The worms are coming in from the root, not off the cap because as I slice crossways, the infestation gets less. I cooked up a mess last night from Paul Stamets video linked above. OMG… slathered on homemade sourdough toast, with fresh lemon garlic asparagus… and Paul’s requisite 100 ml good red wine!!! The tiny ones are so darn cute…
P.S. if there’s only the occasional worm, then I just fry them up and give thanks for the free protein… many cultures still survive on grubs, worms, etc…

Most likely the larvae of the Phorid and or the Sciarid Fly. The eggs are laid in the substrate, from there they consume the underground portion of the mycelium. When mushrooms start growing, they will eat their way up the stem and eventually make their way to the cap. Here they will pupate and then hatch as adult flies from the cap. Look for pinprick holes in the cap to check.  

Most of the damage is occurring at the substrate level. If there are enough of them they may eventually consume the entire mushroom patch from the inside, killing it. There's more info about them, plus what to do here: https://mycobio.co.nz/mushroom-growing-pests-what-to-look-out-for/

Some commercial mushroom growers use nematodes as a biological agent to deal with them. I use yellow sticky flytraps to try and keep the adult population under control, so less egg-laying.

They're okay to eat, they've been living and eating mushrooms all their life! We usually refrigerate the harvested for a few hours, in a plastic container (using paper for longer-term storage. The cold forces them out, as does soaking in salty water.

On harvesting, as soon as we harvest mushrooms we put them in plastic containers. These are lined with kitchen cloth (used for catering) to prevent condensation. After the mushrooms are harvested their respiration rate increases tremendously, and the plastic container allows a buildup of CO2 which will quickly put the mushrooms to sleep. This, plus dropping the temp to just above freezing will allow a longer storage life. If you like, you can move them into paper bags after 24 hours.

Hope this helps

Thank you Brent for adding this on to the thread! I'm mentally bookmarking your response for future reference. I hope the flies don't colonize the whole patch!

Soak 1/4 of a mosquito dunk in a gallon of water for 24hrs and use it to water your mushrooms. That should take care of the fungus gnats. The dunks are organic.

Also note that mushrooms (specifically mushrooms with determinate growth, including Wine Caps), have already formed most of their cells in the button stage, and most growth after this point is just cells expanding with water. Therefore, you're not loosing much by harvesting them when young.

In my experience, maggots in Wine Caps get progressively worse as the season goes on, with the first flush in the spring being maggot-free. I've wondered whether removing old mushrooms (including those of other species) from the garden might help control the fly population?

Whenever I pick some that are too far gone with maggots to be worth eating, I either turn them into slurry to inoculate fresher areas of mulch or feed them to the chickens. The critters probably don't survive that process.